crux-mir: Avoid pointer arithmetic in vec::IntoIter

[qsctr]

We do the same thing as 69e92cb for vec::IntoIter.

Fixes #1144.

[qsctr]

@RyanGlScott Is there a place to put the test case? I saw there is crux-mir/test/symb_eval/alloc but the tests in there seem to be for allocate from the crucible crate and not the standard Rust alloc.

[RyanGlScott]

Thanks, @qsctr!

Is there a place to put the test case? I saw there is crux-mir/test/symb_eval/alloc but the tests in there seem to be for allocate from the crucible crate and not the standard Rust alloc.

Indeed, all of the test cases in the symb_eval subdirectly rely on symbolic branching in some way. The test case in #1144 (comment), however, is entirely concrete. For that reason, I'd favor placing the test case under crux-mir/tests/conc_eval. I'm not picky about which conc_eval subdirectory to use—something like conc_eval/vec should be fine.